Dilated cardiomyopathy (DCM) comprises a group of myocardial disorders that lead to left ventricular dilatation and systolic dysfunction (abnormality of contraction). DCM can be subdivided into ischemic (attributed due to coronary artery disease) or non-ischemic (primary diseases of the myocardium). Hereafter, DCM refers to non-ischemic primary diseases of the myocardium. DCM can be assigned a clinical diagnosis of “idiopathic” DCM if no identifiable cause (except genetic) can be found. Idiopathic DCM can be further subcategorized based upon whether a genetic cause can be identified. Mutations in over 30 genes, including sarcomere genes, perturb a diverse set of myocardial proteins to cause a DCM phenotype. Epidemiologic data indicate that approximately 1 in 2,500 individuals in the general population have idiopathic DCM.
Sarcomere gene mutations that cause DCM are highly penetrant, but there is wide variability in clinical severity and clinical course. Some genotypes are associated with a more malignant course, but there is considerable variability between and even within families carrying the same mutation. While many patients with DCM report minimal or no symptoms for extended periods of time, DCM is a progressive disease with a significant cumulative burden of morbidity and mortality. The hallmark of DCM is a dilated left ventricle, more spherical in shape than usual, and with decreased systolic function. Patients usually present with symptoms of heart failure: dyspnea, orthopnea, exercise intolerance, fatigue, abdominal discomfort and poor appetite. Signs include sinus tachycardia, a gallop rhythm, murmur of mitral regurgitation, rales, jugular venous distension, hepatomegaly, peripheral edema and cool extremities can be found. As with many other disorders, symptoms tend to worsen with age. The patient journey is punctuated by hospitalizations for decompensated heart failure and an increased risk for sudden arrhythmic death and death from pump failure.
Diagnosis is dependent upon patient history and physical examination. Plasma biomarkers such as B-type natriuretic peptide (BNP) or its N-terminal pro-protein (NT-proBNP) can help with diagnosis and management of DCM, especially to distinguish heart failure from comorbid pulmonary disease. Coronary angiography can identify if heart failure is due to ischemic etiology. Endomyocardial biopsy can distinguish DCM from disease processes that might require alternative management strategy, such as myocarditis, storage disease, sarcoidosis or hemochromatosis.
Medical therapy remains the mainstay in patients with DCM and heart failure. Beta-blocker, ACE inhibitor or ARB, mineralcorticoid receptor blocker, and loop diuretics continue to be standard treatment options for the treatment of heart failure symptoms and reduction of risk for cardiovascular death and heart failure hospitalization. Implantable cardioverter defibrillators (ICD) for patients with left ventricular ejection fraction of less than 30% can reduce sudden arrhythmic death. Additionally, cardiac resynchronization therapy (CRT) has been shown to improve heart failure-free survival in select patients. Despite these interventions, morbidity and mortality for heart failure remain high, and hospitalization for heart failure remains the most common reason for hospitalization in the elderly. The present invention provides new therapeutic agents and methods that remedy the unmet need for improved treatment of DCM and related cardiac disorders.